External powder scarfing process and apparatus



Dec. 16, 1952 F. MOESINGER, JR

EXTERNAL POWDER SCARFING PROCESS AND APPARATUS 3 Sheets-Sheet 1 FiledApril 18, 1950 INVENTOR FRED MOESINGER,JR.

ATToRNEY Dec. 16, 1952 MOESINGEYRQ, JR 2,622,048

EXTERNAL POWDER SCARF'ING PROCESS AND APPARATUS Filed April 18, 1950 3Sheets-Sheet 2 POWDER I I Z4PREHEAT/Z5 I W INVENTOR 20 W FREDMOESINGER,JR.

Dec. 16, 1952 F. MOESINGER, JR 2,622,048

EXTERNAL POWDER SCARFING PROCESS AND APPARATUS Filed April 18, 1950 3Sheets-Sheet 3 INVENTOR FR-ED MOESINGER,J R.

ATTORNEY Patented Dec. 16, 1952 Ex'rERuAI.

POWDER SCARFING rRooEss AND APPARATUS Fred Moesinger, Jr., Morristown,N. J assignor, by mesne, assignments, to Union Carbide and CarbonCorporation, a corporation of New York Application April 18, 1950,Serial No. 156,652

Claims.

This invention relates to thermochemical scarfing, and more particularlyto refractorymetal body scarfing with externally fed powdered solidfuel.

In prior attempts to thermochemically scarf stainless steel with the aidof powdered iron, the latter was fed to the reaction zone internally, i.e., along with the scarfing oxygen stream. When internal powder feedequipment was used for scarfing stainless steel slabs, the process wasexpensive, and the surface quality of products rolled from scarfedslabswas not satisfactory in that a type of defect called a shiner was foundto have frequent occurrence upon the rolled scarfed product. A shiner isa slightly depressed area of higher reflectivity with substantially thesame composition as the base material. It is believed that heavy scalerich in admixed iron and possibly covering a metallic deposit on theplate itself is rolled into intimate contact with the underlying metal,thereby protecting it from furnace gases and air. Upon pickling, thethin rolled-in, metallic-scale layer is removed, exposing the protectedzone which is the shiner. .Thus, it was necessary to mechanically grindthe resulting surface in order to avoid undesirable shiners in the finalproduct, thereby considerably increasing the cost. Also, such scarfinginvolved critical process factors; such as critical powder feed rate,and the resulting cut contours were not subject to satisfactorypredetermined control.

In scarfing with an internal fed stream of powder in the past, suchstream was usually round. As a result, a relatively deep groove wasformed in each scarfing pass, so that it was necessary to V subsequentlyremove considerable metal, which was expensive, in order to obtain adesired relatively flat, scarfed surface. This trouble was accentuateddue to the fact that the edges or borders of the groove were uneven,

' which was highly objectionable. In attempting to scarf with parallelstreams of scarflng oxygen containing internally fed powder, in onepass, the adjacent streams interfered with one another, and theresulting scarfed surface had fused powder globules on the ridgesbetween the grooves or cuts, which made the product obviouslyunacceptable for subsequent rolling.

' Another difficulty with prior attempts to scarf 2 1 stainless steelwas due to inherent limitations in the available powder dispensingequipment. Control of the powder flow was restricted to a criticalrange. Furthermore, a single bleeder valve was used to adjust both thepowder carrier gas back-pressure and the carrier gas powderinjectorpressure, which objectionably restricted the range of adjustment. Thecontrol was critical and the powder flow was non-uniform and limited inquantity.

Also, prior to the invention, powder distribution across a single or amultiple stream scarfin cut was non-uniform, due to the inherentconcentration of the powder in the center of a single round stream, aswell as non-uniform blending of the powder in adjacent streams Prior tothe present invention, therefore, it was necessary to mechanically grindor. chip stainless steel slabs, for example, to condition the surfacefor subsequent treatment. This was expensive, slow, and not entirelysatisfactory for all grades of stainless steel. Prior attempts tothermochemically scarf stainless steel shapes were even more expensive.

The main object of this invention, therefore, is to provide animprovedpowder-assisted thermochemical scarfing process which overcomessuch problems. Another object of the invention is to provide apparatusfor thermochemically scarfing hard-to-scarf metal bodies with theassistance of externally-fed powdered solid fuel, which is efficient andeffective; substantially increasing the speed of scarfing while, at thesame time, considerably reducing the consumption of powder. Anotherobject is to provide an improved powder dispenser which can beaccurately adjusted over a relatively wide range. A, further object isto provide means for discharging a relatively flat stream of powder inwhich the powder is substantially uniformly distributed thereacross. Astill further object is to provide an improved semi-finished, stainlesssteel product.

According to the invention there is provided a novel process forthermochemically scarfing hard-to-scarf metal work with the aid ofpowdered solid fuel, which comprises applying a relatively flat streamof commercially pure oygen against the work surface at an acute dihedralangle, applying preheat to the work adjacent such oxygen stream;directing at least one separate, continuous relatively flat stream of asuitable carrier gas containing relatively fine powdered solid fueltoward such oxygen stream at an acute dihedral angle therewith, at alower velocity than that of the oxygen stream, so that the powder mergeswith the leading fringe only of the oxygen stream on the way of thelatter toward the work; and relatively moving the work and such streamsalong the path to be scarfed. The powdered solid fuel is uniformlydistributed across the relatively flat carrier-gas stream, but does notenter into the main layer or core of the oxygen stream due to the highervelocity of the latter.

As a result, substantially all of the powdered solid fuel is heated toignition temperature, and the so-heated particles then burn in theoxygen and liberate energy in the form of heat. Such liberated energyheats the metal being scarfed and the burning powder attacks such metal,raising the temperature and lowering the melting point of the surfacematerial. As a result, the subsequent core of pure oxygen efiicientlyand effectively attacks the metal chemically and physically, removing aportion of the work surface. The reaction zone is then moved along adesired path to be scarfed at a relatively rapid rate, so that the workis thermochemically desurfaced.

scarfing passes up to six times wider than was heretofore possible. areaccomplished by the invention at scarfing speeds which are two to threetimes faster, and with to 75% less powder consumption. Productionoperations also show that the cost has been reduced as much as 50%compared with grinding.

More specifically, according to the invention,

, there is provided apparatus for thermochemically scarfinghard-to-scarf metal work with the assistance of powdered solid fuel,which .comprises the combination of a blowpipe nozzle having arelatively flat continuous slot for discharging a stream of commerciallypure oxygen against the work, and upper and lower rows of 7 ports fordischarging preheating flame supporting jets of gas adjacent suchscarfing oxygen stream, and a novel powdered solid fuel nozzle mountedadjacent the blow-pipe nozzle. Such powdered solid fuel nozzle isprovided with a relatively fiat continuous slot for discharging thepowdered solid fuel in a relatively flat stream of a suitable carriergas separate from the scarfing oxygen, so that the powdered solid fuelfirst passes into the preheating flames, then against the scarfingoxygen stream, and finally against the work being scarfed. Means areassociated with the powdered solid fuel nozzle for assuring uniformtransverse distribution of the powder in the carrier gas upon itsdischarge.

, 'ondfthroug'h a relatively narrow slot which is between 0.0150 and0.0625 inch thick.

. and free of powder.

Adjustable powder dispenser means are also provided for supplying aselected amount of powdered solid fuel in a carrier gas, at a selectedflow rate of the carrier gas, such rate and amount being independentlyadjustable over relatively Wide ranges.

The remarkable increase in process efficiency and speed with externalfeed, according to the invention, is probably the result of providing ahigher degree of oxidation of the adjuvant powder. This may be explainedon the basis that, in scarfing according tov the invention withexternally fed powder, the transfer velocity of the powder from thepowder nozzle to the work is much lower than with the prior internalfeed; allowing more time for the powder to reach ignition temperature,and leaving a layer of scarfing oxygen of higher velocity that isrelatively pure Of even greater importance in quickly and eificientlybringing the powder up to the ignition temperature is the introductionof the powder into or through the preheat flames. On the other hand,with the prior internal feed, the powder was carried to the reactionzone in the relatively cold scarfing oxygen stream, thus contaminatingthe latter and providing no opporherent metallic particles.

tunity for advance ignition and, in addition, a considerable portion ofthe powder was carried in the trailing edge of the oxygen stream, wherecomplete combustion was not accomplished. With external powder feed,according to the invention,however, most of the powder is thrown towardthe work in advance or in the leading edge of the oxygen stream in suchmanner that there is alesser penetration of the oxygen stream andgreater concentration of the reacting powder at the leading edge of theoxygen stream which is then exposed to oxidation by the main body of theoxygen stream which is substantially pure and uncontaminated. As aresult a relatively pure layer or wedge of scarfing oxygen follows andcleans .up the reaction wave in advance thereof. The uniformcross-distribution of the powder also greatly aids complete combustionof the powder where this accomplishes the most good.

The resulting semi-finished product is a stainless steel body having arelatively thin surface scale consisting of a complex oxide having arelatively high ferrosoferric oxide content that is substantially freeof admixed metallic particles, which body also is substantially free ofad- Shiners are eliminated, so that grinding is unnecessary.

In the drawing:

Fig. 1 is a view mainly in side elevation, parts being broken away andshown in section, of a scarfing machine illustrating the invention;

Fig. 2 is a View mainly in front elevation of the apparatus shown inFig. 1;

Fig. 3 is an enlarged fragmentary perspective view of the nozzle portionof such apparatus;

Fig. 4 is an enlarged fragmentary detail, mainly in cross-section,showing how th gas mixture is supplied to the preheating gas ports;

Fig. 5 is a flow diagram of the novel powder dispenser system of theinvention;

, and a battery of tubes 30.

'I2 of conventional construction, like that disclosed in Patent No.2,483,479 to H. T. Smith et al.,

for example. The nozzle [2 is preferably of the wide-continuous-slottedtype having a relatively wide slot I4 for discharging a relatively fiatstream 20 of commercially pure oxygen against the work W, as well asupper and lower rows of ports I5 and I8 for discharging preheating-flamesupport- 7 ing jets of premixed oxy-acetylene gas adjacent such scarfingoxygen stream. The burning gas jets merge into preheating flames 22 and24 which extend above and below the oxygen stream 20,

' forming dihedral angles with the work surface Oxygen is supplied tothe nozzle I2, for example, from a suitable source of oxygen underpressure, by way of a supply pipe 26, a manifold 28 At the same time, asuitable combustible mixture of oxygen and acetylene, or other fuel gas,is supplied to the preheating flame ports I6 and I8 'by way of gas pipes32 which are connected to suitable gas mixers and supplies of oxygen andfuel gas under pressure.

Th powder nozzle I is mounted by a suitable bracket 33 directly on theblowpipe nozzle I2, and comprises a metal base 34 and a metal cover 36secured together by bolts 38. The base 34 and. the cover 36 are providedwith a channel, or mating channels, forming a slot 40 for discharging asuitable relatively fiat powder-laden carrier gas stream 39, which canbe any suitable gas, such as air, or nitrogen, or oxygen, for example.The

discharge face of the powder nozzle I0 is tapered and positioned on theblowpipe nozzle I2 50 that slot 40 discharges the separate powder-ladencarrier gas stream 30 from a flat orifice 4I located directly above thefront-upper edge of the nozzle I2. The powder-laden gas stream 39 formsa dihedral angle with the oxygen stream 20, and with the work surface25.

The upper and lower walls of the slot 40 diverge slightly upstream, andthe upper end of the slot is in communication with the outlet end of anovel powder distributor 42 made of sheetmetal in the form of a fishtailwhich is supported in front of the oxygen manifold 28 by a bracket 44.The interior of the powder distributor 42 has side walls 46 whichdiverge in the direction of the powder now, and front and rear walls 48which gradually converge in the direction of such flow.

. The illustrated powder distributor 42 is provided at the upper endthereof with an angulated tubular inlet 50 for assisting in the properdistribution of powder transversely of the carrier gas stream. Suchinlet 50 is connected by a hose to a novel powder-laden carrier-gassupply system. As shown in Fig. 5, the powder-laden carrier-gas supplysystem includes a novel powder dispenser 52 in the form of a gas-tighthopper containing a suitable supply of solid-fuel powder P, in this caserelatively fine ferrous metal powder. The powder dispenser 52 comprisesa suitable cover 54 provided with a gas pressure relief valve 56. Thedispenser is supported by legs 58 and has a funnel-shaped bottom portion 60 which guides the powder P toward an outlet from which depends aflexible tube 62 provided with a pinch-type shut-off valve 64 which isconnected to a diaphragm 66 by a rod {The powder supply system isdesigned so that of air under pressure.

the powder flow from the dispenser 52 through the outlet 62 and valve64, can be adjusted over a relatively wide range independently of thecarrier or transporting gas flow from the dispenser outlet to the powdernozzle I0, so that the rate of the gas flow also can be adjusted over arelatively wide range, and the powder hose 5I and In one position of thevalve I8 air under pressure is supplied to the diaphragm 66, causing thevalve 64 to close; while in its other position the valve I8 shuts offthe air inlet pipe 82 and connects the pipe to an air exhaust pipe 84,causing the valve 64 to open.

The carrier gas from a suitable source of supply under pressure, entersthe system through an inlet pipe 86 and is split into two unequalstreams by a T-fitting 88. The smaller stream flows through a pipe 90containing a gas pressure regulator 92, the outlet end of the pipe 90being connected to the interior of the dispenser 52 above the powder P.Here the carrier gas exerts a positive pressure on the top of the powderP. The main carrier gas stream, however, flows through a suitable pipe93 containing a gas pressure regulator 94 and a critical orificefiowmeter 96 which,

with regulator 94, controls the main powder transporting gas streamfinally entering a chamber 98 on the downstream side of the powderdispenser 52.

. The powder flow rate is controlled by the size of the orifice oroutlet 62 at the bottom of the dispenser, and the gas pressuredifferential across such orifice. The flow rate in pounds per minute isa substantially straight line function of this differential pressurewhich is indicated by a differential pressure gauge I00 in a pipe I02having one end connected to the pipe 90 and other to the pipe 93. GaugeI00 measures the difference in pressure between space PH above powder P,and space PD in chamber 98. The pipe I02 is also provided with a hopperinlet pressure gauge I04 and a discharge pressure gauge I06. Actualpowder fiow may be determined by consulting a chart or curve based onthe straight line function of the differential pressure.

Thus, each gas stream is controlled independently of the other. In thisway the flow of carrier gas can be accurately adjusted without changingthe flow of pressurizing gas to the hopper, and vice versa. This permitsadjustment, at will, of the density of the powder-air mixture leavingthe dispenser and also adjustment of the velocity of the powder, givinggreater latitude to the control of all important variables.

In operation, the powder leaves the dispenser 52 through orifice 62,passing through the pinchtype diaphragm-operated valve 64--the on-offoperation of which is controlled by the solenoid operated air valve I8.Leaving valve 64 the powder is picked up in chamber 98 by the carriergas stream and enters, through the funnelled is providedwith a tubularshaped inlet 50 which is angulated with respect to the distributor, sothat the powder flow impinges at an abrupt angle against the back wallof the fan-shaped body proper of such distributor. This change ofdirection plus the flattening out of the passage, distributes the powderuniformly across the confined stream. The distributor contains afanshaped interior approach section terminating in an exit slot III]which is in communication with the inlet end of the slot 40 in thepowder nozzle Hi, the parts being secured together in gas-tight relationby an escutcheon I I2. The powder nozzle which receives the powder whichhas been uniformly spread out by the action of the distributor 42 hasdownwardly convergent upper and lower walls in the slot 40 whichdischarges the powder through the exit orifice 4| which, in theillustrated apparatus, is about 0.03 inch by 6.00 inches in size, andthen through the upper preheating flames 22 of the scarfing nozzle l2.In the present example the scarfing nozzle I2 is provided with ascarfing oxygen slot M which is also about 6.00 inches wide.

The following table discloses typical performance data for 6-inch and2-inch wide scarfing equipment.

PERFORMANCE DATA Nozzle size 6-inch unit 2-inch unit Out depth, inches.125 .250 .05 .10 Powder feed rate, lb./min 0. 0 7.0 2. 2. 5 Powderconsumption, lb./sq. it 0. 69 0.70 0. 38 0. 74 Oxygen consumption, cu.ft./sq. ftl 44 73 24 46 Acetylene consumption, on. it-Jsq. it. 1.0 1. 0.66 1.30 Scarfing time, hrJsq. ft .0013 .0017 .0025 .005 Scarfing speed,ft./min 26 18 Air flow, cu. ft./l1r 1,500 1, 500 500 500 Air velocity(discharge), it./scc 350 350 350 l 350 I l The following table disclosesratios for dinerent units.

G-IN. UNIT Cut de th Cu. It. oxygen] Cu. it. acetylene/ Cu. ft. air/lb.

-3 1b. powder 1b. powder powder 0. 125 44/0. 69 63. 8 1. 0/0. 69 =1. 451500/540=2. 78 250 73/0. 70=l04. 3 1. 40/0. 70 2. 0 MOO/420 3. 57

Z-IN. UNIT In the illustrated apparatus (6" unit), at an exit velocityof between 30 and 350 feet/second, the impingement angle of the powderstream on the preheating flames, i. e., the optimum included anglebetween the powder nozzle l0 and the continuous slotted oxygen nozzle i2is about 40, when the exit velocity of the latter is between 500 and 850feet/second. In other words, the slotted scarfing nozzle makes anoptimum dihedral angle of 30 with the top surface of the work, and thepowder nozzle makes an optimum dihedral angle of 70 with the top surfaceof the work.

The following table, when considered in connectionwith Fig. '7,discloses optimum nozzle arrangements in connection with actualperformance data of various units.

'8 OPTIMUM DIHEDRAL ANGLES AND PERFORMANCE DATA 6 unit 2 unit 1 /64"unit 5 degrees.. 30 30 45 d 40 20 30 H .inches. 1%

Oxygen slot size inches 6X z 2 A 1 /ieX ic Powder Slot size do 6%)(0.030 2%X0. 030 1%X%4 Cut depth in l3 25 .05 10 .040 l3 Scariing speed,

F. P. 1V1 l 26 20 35 18 25 15 Oxygen flow, 0. F. H 30, 000 43, 000 9,000 9,000 4, 400 4, 400 Powder flow rate,

lb./min D 7 2. 5 2. 5 l. 5 1. 5 Preheat gas flow,

Actual tests with a 6-inch unit (having a slot width or thickness ofbetween 0.0150 and 0.0625 inch) have revealed that the following rangesfor the dihedral angles a and s with respect to the top surface of thework W are possible (without consideration for quality, but withdefinite propagation of the scarfing out) Anglse ({singlef scar powdering Remarks nozzle nozzle Degrees Degrees 50 18 Minimum. 78 38 Maximum.

CHEMEICAL COMPOSITION Percent Free iron-At least 85.00 Total carbon-Notover .30

Residual material, balance.

PHYSICAL PROPERTIES [Free from any contaminating materials as, forexample, wooden splinters, fibers, or non-ferrous alloys of brass andbronze] Screen size Percent 100 on 200 mesh 25 200 on 325 mesh 25 -32550 Scarfing speeds (i. e., relative movement between the work and thescarfing unit) obtained according to this invention, that to say, 15-50feet/minute, are up to six times faster than when using a prior singlenozzle powder scarfing machine with internal powder feeding. This isaccomplished with 25 to 75% less powder consumption per unit of scarfedsurface. The invention also eliminates shiners in stainless steel sheetsrolled from slabs scarred with powder consisting essentially of iron,without mechanically grinding the scarfed surface before final rolling.The invention, furthermore, results in a surface of good quality in theas-scarfed condition, i. e., such that it may be rolled into a finishedshape, requiring a minimum of additional conditioning.

9 The scale I I4 that-remains adhering to the base metal H6 or the workW, Fig: 6, has a very high degree of oxidation. There is practically noFeO, and substantially or mainly all of such scale is Fe3O4. Theoxidation products are substantially free of admixed metal (particularlyiron or ironrich metallic compounds). The scale layer may be classifiedas light. When the base metal H6 is stainless steel, its surface isrelatively free-of slag and shows only a typical melted condition of thesurface on the order of magnitude of 0.005 inch, or less, in thickness.The base metal also is substantially free of metallic particles,deposited on, or adhering to its surface. I ,V

The. scale H4 adhering to the base metal H6 is not. tightly bonded; andhas littletendency to adhere during subsequent heating, rolling andprocessing. Further, the scaleis quite uniform in .distribution,compositionand adherence, and is of such a nature that subsequentheating and rollingproduces practically no tendency to force the scale 1l4 intojintimate contact with the base metal H6. Thus, the resultingproduct,'.when rolled, is free of, shiners, the mechanical grinding stepbeing entirely eliminated. Furthermore, this is accomplished withconsiderably less powder at a much faster rate and substantially lesscosttha'n was possible prior to the invention Matter disclosed in thepresent case is claimed in my divisional application, Serial No.281,841, filed April 11, 1952, for Refractory-Metal Body ScarfingPneumatic Powder Dispensing Apparatus and Process. V.

I claim:

1. Process of desurfacing a. refractory'metal body, which comprisesapplying preheat to a local surface portion of such body, discharging a,relatively'flat stream .of oxidizing gas at 'an acute angle against suchheated portion, and discharging a separate continuous'relatively flatstream ofgas containing uniformly transversely distributed powderedsolid fuel at an acute angle toward such oxidizing gas stream, so thatthe central planes of such streams in the direction of fl w. thereofform dihedral angles with one another and with such surface i portionofthe body, and relatively moving the body and such streams so thatsuccessive surface portions thereof are progressively removedthermochemically by the combined scarfing action of the powdered solidfuel and oxidizing gas stream.

2. Process of thermochemically scarfing a refractory metal body, whichcomprises applying a relatively fiat stream of oxygen at an acute angleagainst a surface portion of such body, applying a preheating flameagainst such portion adjacent the oxygen stream, directing a continuousrelatively flat stream of iron-powder laden gas in which the powder isuniformly distributed transversely thereof toward such oxygen stream atan acute angle, said relatively fiat streams of oxygen and iron-powderladen gas forming dihedral angles with each other and with such surfaceportion, the velocity of the iron-powder laden gas stream before thepowder enters such flame being less than that of the oxygen stream, andrelatively moving the body and such streams so that successive portionsof the surface are progressively scarfed thereby.

3. Process of conditioning the surface of a cold stainless steel body,which comprises simultaneously scarfing a surface portion from such bodyand leaving the scarfed surface with a relatively thin complex oxidescale which contains a relatively high content of ferrosoferric oxide,

which body is substantially free of adherent stream thereof, wherebycombustion of such iron powder takes place inthe fringe of oxygenadjacent and ahead of such surface portion as the latter is scarfed,leavingsuch metallic particle- I'ree scale on the scarfed surface.

4. In the art of thermochemically scarf ng work composed of metalhavinga refractory oxide surface, such as stainless steel, with the aidof ferrous metal powder, the improvement which comprises irect ng at anexit velocity of between 500 and 850 feet/second a relatively flatstream of commercially pure oxygen against a surface portion of the workto bescaried atan acute dihedral angle with respect to such surfaceportion, directing a preheating flame toward such portion, directingexternal y of said oxygen stream at an exit velocity-of between 30and350 feet/second a separate continuous relatively flat stream ofuniformly transversely distributed ferrous metal powder toward theleading surface of such oxygen stream at acute dihedral angleswithrespect to said oxygenstream and such surface portion, and relativelymoving the body and such streams at a speed of between 12 and 50feet/minute, whereby most of the ferrous metal powder burns in theoxygen at the front of the portion which is subsequently removedby themain stream; of oxygen,- leaving a scarfed surface which issubstantially free of -,adh erent metallic particles. r I

5. In the art of'ther nochemically scarfin g work composed of refractorymetal with :the, aidv of ferrous metal powder, the improvement whichcomprises directing a relatively fiat stream 'of commercially pure.oxygen against: asurface .portion ;of the work to be scarfed at .anacute di-l hedral angle with respect to such surface portion, directinga preheating flame toward such portion, directing externally of saidoxygen stream a separate continuous relatively flat stream of uniformlytransversely distributed ferrous 'metal powder toward the front surfaceof such oxygen stream at acute dihedral angles with respect to saidoxygen stream and such surface portion,

' and relatively moving the body and streams,

whereby the ferrous metal powder burns in the oxygen at the front of theportion which is subsequently removed by the main stream of oxygen,leaving a scarfed surface which is substantially free of adherentmetallic particles. v

6. In the art of thermochemically scarfing work composed of refractorymetal with the aid of combustible metal powder, the improvement whichcomprises directing a stream of commercially pure oxygen against asurface portion of the work to be scarfed at an acute angle with respectto such surface portion, directing externally of said oxygen stream aseparate continuous stream of combustible metal powder toward theleading surface of such oxygen stream at acute angles with respect tosaid oxygen stream and such surface portion, the metal powder beingsubstantially uniformly distributed transversely of the flow thereof,and relatively moving the 11 body and such streams, whereby themetalpowder burns in the oxygen at the work surface direct! ly in frontof the portion which is subsequently removed by the main stream ofoxygen, leaving a scarfed surface which is substantially free ofadherent metallic particles.

7, Apparatus for thermochemically scarrin stainless steel work with theassistance of relatively fine ferrous metal powder, which comprises thecombination of means for applying a relatively flat stream ofcommercially pure oxygen and preheating flames obliquely against andalong the work surface at an acute dihedral angle relative thereto, andmeans for simultaneously applying a relatively flat stream of uniformlytransversely distributed relatively fine ferro'us metal powder obliquelytoward such work surface at a different acute dihedral angle relativethereto, whereby the work surface is thermochemically scarfed by thecombined action of such preheating flame, oxygen, and ferrous metalpowder.

8. Apparatus for thermochemically scarfing refractory metal work withthe assistance of powdered solid fuel, which comprises means forapplying a relatively flat stream of oxygen against the work at anincluded acute dihedral angle with the work surface, means forpreheating the work surface adjacent such oxygen stream, and means fordirecting a separate continuous relatively fiat stream of carrier gascontaining uniformly transversely distributed relatively fine solid fuelpowder toward the work surface at an included acute dihedral angletherewith. I

9. Apparatus for thermochemically scarfing refractory metal work withthe assistance of relatively fine adjuvant powder, which comprises thecombination of a blow-pipe nozzle having a relatively wide continuousslot for discharging a relatively fiat stream of sc'arfing oxygenagainst the work, and upper and lower rows of ports for dischargingpreheating flame supporting jets of combustible gas adjacent such oxygenstream, and a powder-laden gas nozzle having a relatively widecontinuous slot for discharging a continuous relatively flat stream ofcarrier gas containing uniformly transversely distributed relativelyfine powder first through at least one row of such flames, then againstsuch oxygen stream and finally against the work.

10. Apparatus for thermochemically scarfing metal work with theassistance of relatively fine ferrous metal powder, comprising apowder-laden gas nozzle having a relatively wide continuous slot fordischarging a continuous relatively fiat stream of gas containinguniformly transversely distributed relatively fine metallic powderagainst the work, said slot having upper and lower walls which divergeupstream, and a fan-shaped distributor connected to said nozzle, saiddistributor having side walls which converge upstream, and front andrear walls which diverge upstream with respect to the powder flow, sothat the powder is uniformly distributed in the carrier gas stream whichis finally discharged from such slot, and metallic powder-laden gassupply means connected to the upper end of said fan-shaped distributor.

FRED MOESINGER, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 851,668 James 1 Apr. 30, 19072,042,428 Krekeler s May 26-, 1936 2,137,968 Tanner Nov. 22, 19382,267,405 Jones et al. Dec. 23, 1941 2,327,337 Burch et al. Aug. 24,1943 2,444,899 Meincke et al. July 6, 1948 2,444,900 Meincke et al. 1July 6, 1948 2,451,422 Wagner Oct. 12, 1948 2,465,978 Meincke et al. 4Mar. 29, 1949 2,470,819 Hughey May 24, 1949 2,470,999 Meincke May 24,1949 2,483,479 Smith et al. Oct. 4, 1949 2,487,974 Kirk Nov. 15, 19492,493,802 Bucknam et al. Jan. 10, 1950 2,513,303 Feild 1 July 4, 1950

1. PROCESS OF DESURFACING A REFRACTORY METAL BODY, WHICH COMPRISESAPPLYING PREHEAT TO A LOCAL SURFACE PORTION OF SUCH BODY, DISCHARGING ARELATIVELY FLAT STREAM OF OXIDIZING GAS AT ACUTE ANGLE AGAINST SUCHHEATED PORTION, AND DISCHARGING A SEPARATE CONTINUOUS RELATIVELY FLATSTEAM OF GAS CONTAINING UNIFORMLY TRANSVERSELY DISTRIBUTED POWDEREDSOLID FUEL AT AN ACUTE ANGLE TOWARD SUCH OXIDIZING GAS STREAM, SO THATTHE CENTRAL PLANES OF SUCH STEAMS IN THE DIRECTION OF